Creating Closures with Anonymous Functions in Go

Introduction

In this lab, you will learn how to use anonymous functions to create closures in Golang.

Skills Graph

Closures

You need to create a function that returns another function. The returned function should increment a variable by one each time it is called. The variable should be unique to each returned function.

• The function intSeq should return another function.
• The returned function should increment a variable by one each time it is called.
• The variable should be unique to each returned function.

$ go run closures.go
1
2
3
1

## The last feature of functions we'll look at for now is
## recursion.

There is the full code below:

// Go supports [_anonymous functions_](https://en.wikipedia.org/wiki/Anonymous_function),
// which can form <a href="https://en.wikipedia.org/wiki/Closure_(computer_science)"><em>closures</em></a>.
// Anonymous functions are useful when you want to define
// a function inline without having to name it.

package main

import "fmt"

// This function `intSeq` returns another function, which
// we define anonymously in the body of `intSeq`. The
// returned function _closes over_ the variable `i` to
// form a closure.
func intSeq() func() int {
	i := 0
	return func() int {
		i++
		return i
	}
}

func main() {

	// We call `intSeq`, assigning the result (a function)
	// to `nextInt`. This function value captures its
	// own `i` value, which will be updated each time
	// we call `nextInt`.
	nextInt := intSeq()

	// See the effect of the closure by calling `nextInt`
	// a few times.
	fmt.Println(nextInt())
	fmt.Println(nextInt())
	fmt.Println(nextInt())

	// To confirm that the state is unique to that
	// particular function, create and test a new one.
	newInts := intSeq()
	fmt.Println(newInts())
}

Summary

In this lab, you learned how to use anonymous functions to create closures in Golang. Closures are useful when you want to define a function inline without having to name it.